1. Field of the Invention
The present invention generally relates to an apparatus and a method for monitoring a fetus in a maternal body, and more particularly, to an apparatus for monitoring fetal movements, uterine contractions, and fetal positions.
2. Description of Related Art
The utmost concern of a pregnant woman (also referred to as a maternal body) is that whether the baby she's carrying is healthy and growing normally and whether there is the possibility of a premature delivery. Besides consulting a clinical doctor, a mother-to-be can only determine the status of the fetus based on her own observation (for example, by detecting the number of fetal movements). Accordingly, it is very inconvenient to observe and record the status of the fetus for a long time. Thus, a portable equipment that can automatically detect and record the status of a fetus and provide the position, movement, health, and growth of the fetus through data analysis is desired. With such an equipment, the mother-to-be can submit the data measured at home to her clinical doctor to receive better care. As to a maternal body with an abnormal fetal position, it is the best time to correct the fetal position during the 30th to the 34th weeks of pregnancy. Thus, the portable monitoring equipment should be designed with a fetal position detection function.
Presently, there are many different techniques for monitoring and assessing the health of a fetus before delivery, such as the uterine contraction stress test, the nonstress test, the fetal movement assessment, the biophysical profile, modified biophysical profile (BPP), and the umbilical artery Doppler velocimetry, etc.
In addition, existing techniques for quantitatively analyzing fetal movements include the kick count technique, the Doppler ultrasonic technique, the ultrasonic technique, and the moving coil technique. In the kick count technique, fetal movements are recorded according to the sensation of the maternal body to the fetus. In the Doppler ultrasonic technique, a piezoelectric probe is triggered to emit an ultrasonic wave to a specific area so as to detect the Doppler effect of fetal movements within this area. In the ultrasonic technique, a piezoelectric probe is triggered to emit an ultrasonic wave so as to image the fetus in the abdomen of the maternal body. In the moving coil technique, a moving coil is tied on the abdomen of the maternal body, and when a fetal movement occurs, the moving coil changes by magnetic induction. Each of aforementioned techniques has its own pros and cons.
Moreover, a 4D ultrasonic equipment is the most accurate one among all fetal movement identification equipments and can identify different types of fetal movements. However, a 4D ultrasonic equipment is not suitable for long time use and is very expensive. An abdomen physiological sensor equipment can detect not all but most fetal movements except the respiration of the fetus, and which offers low cost, high portability, and no position adjustment.
FIG. 1 illustrates the basic fetal positions. Referring to FIG. 1(a), the fetus 100 directs its head toward the cervix before delivery so that the head can be delivered first. The fetal position illustrated in FIG. 1(a) is a normal position and which takes up about 96% of all fetal positions. Referring to FIG. 1(b), the fetus 100 has its head directing upwards and his breech directing downwards. This is a very serious abnormal fetal position and takes up about 3% of all fetal positions, and this fetal position needs to be corrected through a complicated process. Referring to FIG. 1(c), the fetus 100 is in a horizontal position. This fetal position takes up about 0.2-0.5% of all fetal positions and is a second serious abnormal fetal position, and which can be corrected through a fetal position correction process some time before the delivery.
FIG. 2 illustrates various directions corresponding to a fetus position. The fetus has different rotation directions. Taking the normal fetal position illustrated in FIG. 1(a) as an example, it has 6 directions including the front and back directions based on the direction of the occipital on the fetus's head. As shown in FIGS. 2(a)-2(f), the 6 directions are respectively denoted as LOP, LOT, LOA, ROP, ROT, and ROA. Similarly, the fetal position illustrated in FIG. 1(b) also has 6 directions. The same method for defining the direction of a fetal position is generally adopted and can be applied to any other fetal position therefore will not be described any further.
FIG. 3 is a cross-sectional view illustrating the directions of a fetal position with respect to a maternal body. Referring to FIG. 3, the maternal body has a backbone 102 and a pelvis 104, and the fetus 106 has a fetal backbone 108. The fetus 106 has different fetal positions according to its direction.
FIG. 4 illustrates a conventional technique of attaching physiological sensors on an abdomen. Referring to FIG. 4, four induction sensors 112 are attached at four different positions of the abdomen 110 of a maternal body. One of the induction sensors 112 is attached under the navel, and the other three induction sensors 112 are respectively attached at a left position, a top position, and a right position, as shown in FIG. 4. An electrocardiogram (ECG) of the fetus can be measured by using the induction sensors 112. FIG. 5 illustrates four conventional electrocardiogram (ECG) categories. An ECG is usually composed of the Q-, R-, and S-waves of the heart, wherein the R-wave is the major analysis object. The wave A in FIG. 5 is an upward triangular wave, the wave B is a downward triangular wave, the wave C is a upward and then downward wave, and the wave D is a downward and then upward wave.
The signal obtained through each measuring lead is categorized into one of the four waveforms illustrated in FIG. 5. Based on clinical data, a fetal position can be obtained by composing the waveforms measured through three measuring leads. A fetal position is categorized according to a combination of several parameters:
X=vertex, brow, face, breech, or shoulder of the fetus
L=left pelvis of the maternal body
R=right pelvis of the maternal body
D=vertical center of the maternal pelvis
A=front half of the maternal pelvis
P=rear half of the maternal pelvis
T=horizontal center of the maternal pelvis
A fetal position is the position of a representative bone of a first delivered part in the maternal pelvis (i.e., the front left portion, the front right portion, the rear left portion, and the rear right portion of the pelvis). The representative bone of vertex presentation is the occipital (O), the representative bone of breech presentation is the sacrum (S), the representative bone of face presentation is the mentum (M), and the representative bone of shoulder presentation is the scapula (Sc).
Each fetal position is expressed in following three parts:
1. left (L) or right (L) depending on whether the representative bone is at the left side or right side of the pelvis;
2. the name of the representative bone (for example, “O” with vertex presentation, “S” with breech presentation “M” with face presentation, and “Sc” with shoulder presentation);
3. the representative bone being at the front of, the back of, or across the pelvis (for example, with vertex presentation, the fetal position is determined to be LOA (which is the most common fetal position) if the occipital is at the left side of the pelvis and faces the front side.
Each fetal position is expressed in short as following:    six fetal positions with vertex presentation: LOA, LOT, LOP, ROA, ROT, and ROP.    six fetal positions with breech presentation: LSA, LST, LSP, RSA, RST, and RSP.    six fetal positions with face presentation: LMA, LMT, LMP, RMA, RMT, and RMP.    four fetal positions with shoulder presentation: LScA, LScP, RScA, and RScP.
However, how to improve the conventional technique of attaching physiological sensors on the abdomen of a maternal body so as to monitor a fetus more efficiently and accurately is one of the major subjects in the industry.